1. Field of the Invention
The present invention relates to a ceramic electronic component and a method of manufacturing the same.
2. Description of the Background Art
Ceramic electronic components represented by stack ceramic capacitors have recently been used in an environment that is more severe than in a conventional example.
For example, electronic components included in mobile devices such as a portable telephone and a portable music player are required to be resistant to shock at the time of a drop. Specifically, electronic components are required not to be detached from a mounting board and to be free from cracks when a drop impact is applied thereto.
Electronic components included in car-mounted devices such as an ECU (Engine Control Unit) are required to be resistant to a shock originating from a heat cycle. Specifically, electronic components are required to be free from cracks in solder used for mounting and in the electronic components themselves when bending stress resulting from thermal expansion and contraction of amounting board originating from a heat cycle is applied thereto.
In order to satisfy the requirements above, use of a thermosetting conductive paste for an external electrode of a ceramic electronic component, instead of a conventional firing-type conductive paste, has been proposed.
WO2004/053901 discloses a stack ceramic electronic component having an external electrode formed of a thermosetting conductive paste.
In the stack ceramic electronic component described in WO2004/053901, an external electrode is formed through plating of an external electrode layer formed of a thermosetting conductive paste containing a resin and metal powders having a melting point not higher than 300° C.
In general, a resin is high in hygroscopicity and tends to absorb moisture. As a resin which has absorbed moisture is heated, moisture is vaporized and water vapor is generated in the resin, and in addition, some of the resin is decomposed to generate a decomposition gas.
In a case that an external electrode is formed through plating of an external electrode layer formed of a thermosetting conductive paste containing a resin as in the stack ceramic electronic component described in WO2004/053901, heating in a reflow step in mounting the stack ceramic electronic component leads to generation of water vapor and a decomposition gas in the external electrode. The water vapor and the decomposition gas are confined by a plating film on a surface of the external electrode.
In a case that a defective portion or a partially thin portion is present in a plating film, the confined water vapor and decomposition gas may burst from the defective portion or the thin portion to the outside of the external electrode. The burst causes such a phenomenon that solder molten in the reflow step is blown off, which is generally called “solder burst”.
In a case that a thermosetting conductive paste is directly applied to a ceramic stack as in the stack ceramic electronic component described in WO2004/053901, moisture contained in the ceramic stack is absorbed in the resin in the external electrode. Then, an amount of water vapor generated during heating increases, and solder burst is more likely.